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KVM: arm64: Add templates for BHB mitigation sequences

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KVM writes the Spectre-v2 mitigation template at the beginning of each
vector when a CPU requires a specific sequence to run.

Because the template is copied, it can not be modified by the alternatives
at runtime. As the KVM template code is intertwined with the bp-hardening
callbacks, all templates must have a bp-hardening callback.

Add templates for calling ARCH_WORKAROUND_3 and one for each value of K
in the brancy-loop. Identify these sequences by a new parameter
template_start, and add a copy of install_bp_hardening_cb() that is able to
install them.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
James Morse 2022-04-06 17:45:42 +01:00 committed by Greg Kroah-Hartman
parent 1451b7fe7a
commit 094a410426
5 changed files with 128 additions and 4 deletions
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3
arch/arm64/include/asm/cpucaps.h
View File

@ -39,7 +39,8 @@
#define ARM64_SSBD 18
#define ARM64_MISMATCHED_CACHE_TYPE 19
#define ARM64_WORKAROUND_1188873 20
#define ARM64_SPECTRE_BHB 21
#define ARM64_NCAPS 21
#define ARM64_NCAPS 22
#endif /* __ASM_CPUCAPS_H */

2
arch/arm64/include/asm/kvm_mmu.h
View File

@ -362,7 +362,7 @@ static inline void *kvm_get_hyp_vector(void)
struct bp_hardening_data *data = arm64_get_bp_hardening_data();
void *vect = kvm_ksym_ref(__kvm_hyp_vector);
if (data->fn) {
if (data->template_start) {
vect = __bp_harden_hyp_vecs_start +
data->hyp_vectors_slot * SZ_2K;

6
arch/arm64/include/asm/mmu.h
View File

@ -45,6 +45,12 @@ typedef void (*bp_hardening_cb_t)(void);
struct bp_hardening_data {
int hyp_vectors_slot;
bp_hardening_cb_t fn;
/*
* template_start is only used by the BHB mitigation to identify the
* hyp_vectors_slot sequence.
*/
const char *template_start;
};
#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR

50
arch/arm64/kernel/bpi.S
View File

@ -73,3 +73,53 @@ ENTRY(__smccc_workaround_1_smc_end)
ENTRY(__smccc_workaround_1_hvc_start)
smccc_workaround_1 hvc
ENTRY(__smccc_workaround_1_hvc_end)
ENTRY(__smccc_workaround_3_smc_start)
sub sp, sp, #(8 * 4)
stp x2, x3, [sp, #(8 * 0)]
stp x0, x1, [sp, #(8 * 2)]
mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
smc #0
ldp x2, x3, [sp, #(8 * 0)]
ldp x0, x1, [sp, #(8 * 2)]
add sp, sp, #(8 * 4)
ENTRY(__smccc_workaround_3_smc_end)
ENTRY(__spectre_bhb_loop_k8_start)
sub sp, sp, #(8 * 2)
stp x0, x1, [sp, #(8 * 0)]
mov x0, #8
2: b . + 4
subs x0, x0, #1
b.ne 2b
dsb nsh
isb
ldp x0, x1, [sp, #(8 * 0)]
add sp, sp, #(8 * 2)
ENTRY(__spectre_bhb_loop_k8_end)
ENTRY(__spectre_bhb_loop_k24_start)
sub sp, sp, #(8 * 2)
stp x0, x1, [sp, #(8 * 0)]
mov x0, #24
2: b . + 4
subs x0, x0, #1
b.ne 2b
dsb nsh
isb
ldp x0, x1, [sp, #(8 * 0)]
add sp, sp, #(8 * 2)
ENTRY(__spectre_bhb_loop_k24_end)
ENTRY(__spectre_bhb_loop_k32_start)
sub sp, sp, #(8 * 2)
stp x0, x1, [sp, #(8 * 0)]
mov x0, #32
2: b . + 4
subs x0, x0, #1
b.ne 2b
dsb nsh
isb
ldp x0, x1, [sp, #(8 * 0)]
add sp, sp, #(8 * 2)
ENTRY(__spectre_bhb_loop_k32_end)

71
arch/arm64/kernel/cpu_errata.c
View File

@ -74,6 +74,14 @@ extern char __smccc_workaround_1_smc_start[];
extern char __smccc_workaround_1_smc_end[];
extern char __smccc_workaround_1_hvc_start[];
extern char __smccc_workaround_1_hvc_end[];
extern char __smccc_workaround_3_smc_start[];
extern char __smccc_workaround_3_smc_end[];
extern char __spectre_bhb_loop_k8_start[];
extern char __spectre_bhb_loop_k8_end[];
extern char __spectre_bhb_loop_k24_start[];
extern char __spectre_bhb_loop_k24_end[];
extern char __spectre_bhb_loop_k32_start[];
extern char __spectre_bhb_loop_k32_end[];
static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
const char *hyp_vecs_end)
@ -87,12 +95,14 @@ static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
flush_icache_range((uintptr_t)dst, (uintptr_t)dst + SZ_2K);
}
static DEFINE_SPINLOCK(bp_lock);
static int last_slot = -1;
static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
const char *hyp_vecs_start,
const char *hyp_vecs_end)
{
static int last_slot = -1;
static DEFINE_SPINLOCK(bp_lock);
int cpu, slot = -1;
spin_lock(&bp_lock);
@ -113,6 +123,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
__this_cpu_write(bp_hardening_data.fn, fn);
__this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start);
spin_unlock(&bp_lock);
}
#else
@ -544,3 +555,59 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
{
}
};
#ifdef CONFIG_KVM
static const char *kvm_bhb_get_vecs_end(const char *start)
{
if (start == __smccc_workaround_3_smc_start)
return __smccc_workaround_3_smc_end;
else if (start == __spectre_bhb_loop_k8_start)
return __spectre_bhb_loop_k8_end;
else if (start == __spectre_bhb_loop_k24_start)
return __spectre_bhb_loop_k24_end;
else if (start == __spectre_bhb_loop_k32_start)
return __spectre_bhb_loop_k32_end;
return NULL;
}
void kvm_setup_bhb_slot(const char *hyp_vecs_start)
{
int cpu, slot = -1;
const char *hyp_vecs_end;
if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available())
return;
hyp_vecs_end = kvm_bhb_get_vecs_end(hyp_vecs_start);
if (WARN_ON_ONCE(!hyp_vecs_start || !hyp_vecs_end))
return;
spin_lock(&bp_lock);
for_each_possible_cpu(cpu) {
if (per_cpu(bp_hardening_data.template_start, cpu) == hyp_vecs_start) {
slot = per_cpu(bp_hardening_data.hyp_vectors_slot, cpu);
break;
}
}
if (slot == -1) {
last_slot++;
BUG_ON(((__bp_harden_hyp_vecs_end - __bp_harden_hyp_vecs_start)
/ SZ_2K) <= last_slot);
slot = last_slot;
__copy_hyp_vect_bpi(slot, hyp_vecs_start, hyp_vecs_end);
}
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
__this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start);
spin_unlock(&bp_lock);
}
#else
#define __smccc_workaround_3_smc_start NULL
#define __spectre_bhb_loop_k8_start NULL
#define __spectre_bhb_loop_k24_start NULL
#define __spectre_bhb_loop_k32_start NULL
void kvm_setup_bhb_slot(const char *hyp_vecs_start) { };
#endif